White House press secretary Sarah Sanders urged people not to jump to conclusions about photos showing White House chief of staff John Kelly's reaction to President Trump's speech Tuesday before the United Nations General Assembly.

"He's part of the speech-writing process and very engaged," Sanders told Fox News on Wednesday morning. "I would certainly not read anything into that picture any more than probably just like the rest of us, we're tired trying to keep up with this president who's working hard every day to help America."

A series of photos taken of Kelly during Trump's speech before the 72nd session of the United Nations General Assembly show Kelly appearing upset during the president's address. In one image, the retired Marine Corps general has his hand pressed to his head. In another, Kelly is looking down at the floor, with his hands clasped together, covering his mouth.

During his speech before world leaders and diplomats, Trump called North Korean leader Kim Jong Un "Rocket Man" and issued a sharp condemnation of the Iran nuclear deal, saying it is an "embarrassment."

But Sanders said Kelly's appearance during the address may be attributed to Trump's high energy, which has left many White House staffers exhausted trying to keep up with him.

"The president has an abundance of energy. I don't know where it comes from," she said. "All of us on the staff are tired trying to keep up with him. I wouldn't be surprised if that's part of it."

The White House press secretary also praised Kelly for the work he's done since taking over for former White House chief of staff Reince Priebus in late July.

"Gen. Kelly's been a great addition to the team. He and the president have great chemistry," Sanders said. "They're working really well together. He's a great leader. I mean, you don't get to be a four-star general and not be a strong leader."